A SiC single crystal manufacturing apparatus has been proposed, for example, in JP-A-2007-176718. In the conventional apparatus, the diameter of the seed crystal is reduced by sublimation etching of the side surface and the outer edge of the seed crystal, where a lot of defects and distortions are likely to exist. Then, the diameter of the seed crystal is increased to a predetermined level by growing a SiC single crystal on the seed crystal. Specifically, the conventional apparatus includes a guide having an inner wall located facing the outer edge of the seed crystal. The inner diameter of the guide is smaller than the diameter of the seed crystal and increases with the distance from the seed crystal so that the diameter of the seed crystal can be increased.
Thus, the conventional apparatus may reduce or prevent defects and distortions on the outer edge of the seed crystal. Accordingly, the SiC single crystal manufactured by the conventional apparatus may have high quality.
However, when the outer edge of the seed crystal is removed by a sublimation etching method, the temperature difference between the SiC single crystal and the guide decreases with the growth of the SiC single crystal. Further, the clearance between the SiC single crystal and the guide increases with the growth of the SiC single crystal. Accordingly, the SiC material gas becomes difficult to flow so that a polycrystal can be grown between the SiC single crystal and the guide. As a result, the polycrystal is adhered to the SiC single crystal so that the quality of the outer edge of the SiC single crystal can be degraded.
Using a SiC single crystal manufacturing apparatus shown in FIGS. 6A and 6B may prevent the polycrystal from being adhered to the SiC single crystal. In the SiC single crystal manufacturing apparatus, the seed crystal where the SiC single crystal is grown is misaligned with a portion where the polycrystal is grown.
Specifically, in FIG. 6A, a seed crystal J2 is placed on a projection J1a of a base J1. Thus, a SiC single crystal J3 that is grown on the seed crystal J2 can be misaligned with a polycrystal J4 that is grown around the projection J1a. However, as the single crystal J3 is grown long on the seed crystal J2, the polycrystal J4 is grown around the projection J1a. Therefore, the polycrystal J4 may be adhered to the single crystal J3. In FIG. 6B, the projection J1a is surrounded by a canopy member J1b to prevent the polycrystal J4 from being grown around the projection J1a. However, as the single crystal J3 is grown long on the seed crystal J2, the polycrystal J4 may be adhered to and grown on the canopy member J1b. The polycrystal J4 on the canopy member J1b may be adhered to the single crystal J3.